About Magnifiers

Magnifiers enlarge the image of an object so that its details may be seen more clearly. This is a function of the power of the magnifier. Three other factors affect the performance of a magnifier and its suitability for certain jobs: field of view, depth of field and working distance (focal length). The four factors are interdependent; if the power is increased, the other three become smaller, and so forth. In selecting a magnifier, you should consider all four factors.

Power of Magnification
The power of magnification refers to the capacity in the lens to increase the image size. X, the symbol used with a number in denoting the power of a magnifier, is quite simply the multiplication sign, “times.” Thus, a 2X magnifier creates an image size twice as large as that which the unaided eye sees at 10 inches. A 3X magnifier triples the image size, and so on.

Focal Length (Working Distance) 
Focal length is the distance at which a magnifier must be held away from an object to achieve clear focus and maximum magnification. In a 2X magnifier the focal length is approximately 5 inches (the lens thickness is a factor); in a 5X magnifier it is 2 inches; and in a 20X magnifier it is 1/2 inch.

Field of View
The size of the area that can be seen at any one time is the field of view. In a magnifier, a number of things influence the field of view: the diameter of the lens for instance. The power of magnification primarily determines the size of the field of view—the higher the power the smaller the field of view.